Surgical instrument including an adapter assembly and an articulating surgical loading unit

ABSTRACT

An adapter assembly of a surgical instrument includes a cam member defining a proximal cam slot and a distal cam slot, a first articulation shaft, and a second articulation shaft. The first articulation shaft has a proximal end portion received in the proximal cam slot, and a distal end portion configured to be coupled to a surgical loading unit. The second articulation shaft has a proximal end portion received in the distal cam slot, and a distal end portion configured to be coupled to the surgical loading unit. The first and second articulation shafts are configured to move in opposing longitudinal directions in response to a rotation of the cam member to articulate the surgical loading unit.

BACKGROUND Technical Field

The disclosure relates generally to surgical instruments for endoscopic use and, more specifically, to surgical instruments including adapter assemblies that articulate an attached surgical loading unit.

Background of Related Art

Various types of surgical instruments used to endoscopically treat tissue are known in the art, and are commonly used, for example, for closure of tissue or organs in transection, resection, anastomoses, for occlusion of organs in thoracic and abdominal procedures, and for electrosurgically fusing or sealing tissue.

One example of such a surgical instrument is a surgical stapling instrument. Typically, surgical stapling instruments include an end effector having an anvil assembly and a cartridge assembly for supporting an array of surgical staples, an approximation mechanism for approximating the cartridge and anvil assemblies, and a firing mechanism for ejecting the surgical staples from the cartridge assembly.

During laparoscopic or endoscopic surgical procedures, access to a surgical site is achieved through a small incision or through a narrow cannula inserted through a small entrance wound in a patient. Because of limited area available to access the surgical site, many endoscopic instruments include mechanisms for articulating the end effector of the instrument in relation to a body portion of the instrument to improve access to tissue to be treated.

SUMMARY

In an aspect of the disclosure, an adapter assembly includes a cam member defining a first cam slot and a second cam slot, an outer tube extending distally from the cam member and having a distal end portion configured to be coupled to a surgical loading unit, and first and second articulation shafts each having a proximal end portion and a distal end portion. The proximal end portion of the first articulation shaft is operably coupled to the proximal cam slot of the cam member and the proximal end portion of the second articulation shaft is operably coupled to the distal cam slot of the cam member. The distal end portion of each of the first and second articulation shafts is configured to be coupled to the surgical loading unit. The first and second articulation shafts are configured to translate in opposite directions in response to a rotation of the cam member to articulate the surgical loading unit relative to the outer tube.

In aspects, the adapter assembly may further include a proximal ring member and a distal ring member each disposed about the cam member. The proximal ring member may have a projection received in the first cam slot, and the distal ring member may have a projection received in the second cam slot. The proximal and distal ring members may be configured to move axially in opposite longitudinal directions in response to the rotation of the cam member.

In aspects, the proximal end portion of the first articulation shaft may be axially restrained to the proximal ring member, and the proximal end portion of the second articulation shaft may be axially restrained to the distal ring member. The first and second articulation shafts may be configured to move axially with the respective proximal and distal ring members.

In aspects, the first and second articulation shafts may be rotatable relative to and about the respective proximal and distal ring members.

In aspects, the proximal ring member may define an outer annular groove therein, and the proximal end portion of the first articulation shaft may have an annular protrusion slidably received in the annular groove. The distal ring member may define an outer annular groove therein, and the proximal end portion of the second articulation shaft may have an annular protrusion slidably received in the annular groove of the distal ring member.

In aspects, the adapter assembly may further include a knob housing disposed about a proximal end portion of the outer tube. The proximal end portion of each of the first and second articulation shafts may be non-rotationally coupled to the knob housing and axially movable relative to the knob housing.

In aspects, the knob housing may include an inner surface defining a pair of longitudinally-extending slots, and the proximal end portion of each of the first and second articulation shafts may have a longitudinally-extending ridge received in the respective pair of longitudinally-extending slots of the knob housing.

In aspects, the proximal end portion of the first articulation shaft may have an inwardly-extending protrusion, and the distal end portion of the outer tube may define a longitudinally-extending slot having received therein the protrusion of the first articulation shaft, such that the distal end portion of the outer tube rotates with the first articulation shaft about the longitudinal axis in response to a rotation of the knob housing.

In aspects, the proximal end portion of each of the first and second articulation shafts may be disposed about the outer tube and the cam member.

In accordance with another aspect of the disclosure, a surgical instrument is provided and includes a surgical loading unit and an adapter assembly. The adapter assembly includes a coupling mechanism having a drive shaft, a cam member operably coupled to the drive shaft and defining a proximal cam slot and a distal cam slot, an outer tube extending distally from the cam member and having a distal end portion configured to be coupled to the surgical loading unit, and first and second articulation shafts each having a proximal end portion and a distal end portion. The proximal end portion of the first articulation shaft is operably coupled to the proximal cam slot of the cam member and the proximal end portion of the second articulation shaft is operably coupled to the distal cam slot of the cam member. The distal end portion of each of the first and second articulation shafts is configured to be coupled to the surgical loading unit. The first and second articulation shafts are configured to translate in opposite directions in response to a rotation of the cam member to articulate the surgical loading unit relative to the outer tube.

In aspects, the adapter assembly may further include a knob housing rotationally coupled to the coupling mechanism and disposed about a proximal end portion of the outer tube. The proximal end portion of each of the first and second articulation shafts may be non-rotationally coupled to the knob housing and axially movable relative to the knob housing.

In aspects, the proximal end portion of each of the first and second articulation shafts may be curved and disposed about the outer tube and the cam member.

BRIEF DESCRIPTION OF THE DRAWINGS

Surgical instruments including exemplary aspects of the disclosed adapter assemblies are disclosed herein with reference to the drawings, wherein:

FIG. 1 is a perspective view of a surgical instrument including a handle assembly, an adapter assembly, and a surgical loading unit;

FIG. 2 is a perspective view of the adapter assembly and the surgical loading unit of FIG. 1;

FIG. 3 is a perspective view of internal components of the adapter assembly of FIG. 2 including a coupling mechanism, an outer tube, a pair of ring members, and a pair of articulation shafts;

FIG. 4 is a perspective view, with parts separated, of the adapter assembly of FIG. 3;

FIG. 5 is a side perspective view illustrating the adapter assembly of FIG. 3, with a portion of the outer tube, the pair of articulation shafts, and the pair of ring members removed to better illustrate a drive assembly and a cam member;

FIG. 6 is a side perspective view illustrating the adapter assembly of FIG. 3, with a portion of the outer tube and the pair of articulation shafts removed;

FIG. 7 is a side perspective view illustrating the adapter assembly of FIG. 3, with the pair of articulation shafts removed;

FIG. 8 is a longitudinal cross-sectional view illustrating the surgical loading unit of FIG. 1 in an articulated position;

FIG. 9 is a side perspective view illustrating the surgical loading unit of FIG. 1 in the articulated position;

FIG. 10 is a longitudinal cross sectional view of the adapter assembly of FIG. 3 illustrating the pair of articulation shafts in a non-articulated position; and

FIG. 11 is a longitudinal cross sectional view of the adapter assembly of FIG. 3 illustrating the pair of articulation shafts in an articulated position.

DETAILED DESCRIPTION

As used herein, the term “distal” refers to that portion of the surgical instrument which is farthest from a clinician, while the term “proximal” refers to that portion of the surgical instrument which is closest to the clinician. In addition, as used herein, the term clinician refers to medical staff including doctors, nurses and support personnel.

The disclosure is directed to a surgical instrument including an adapter assembly configured to be actuated by a hand-held actuator or a surgical robotic system, and a surgical loading unit coupled to the adapter assembly. The adapter assembly includes an articulation mechanism that drives an articulation of the surgical loading unit relative to the adapter assembly. The articulation mechanism includes a rotatable cam member that defines a pair of cam slots, each of which receiving a corresponding pin of a pair of ring members. As the cam member rotates, the cam slots drive an opposing longitudinal motion of the pair of ring members, which translate first and second articulation shafts in opposing longitudinal directions. Translation of the articulation shafts in opposite longitudinal directions articulates the surgical loading unit relative to an outer tube of the adapter assembly. Additional advantages of the disclosed surgical instruments and components thereof are described below.

FIGS. 1 and 2 depict a surgical instrument 10 including a handle assembly 12, an adapter assembly 20 configured to be coupled to the handle assembly 12, and a surgical loading unit 30 pivotably coupled to the adapter assembly 20. While the depicted surgical instrument 10 may be configured to fire staples, it is contemplated that the surgical instrument 10 may be adapted to fire any other suitable fastener such as clips and two-part fasteners. Additionally, while the figures depict a linear surgical stapling instrument 10, it is envisioned that certain components described herein may be adapted for use in other types of endoscopic surgical instruments including non-linear surgical stapler loading units, endoscopic forceps, graspers, dissectors, other types of surgical stapling instruments, powered vessel sealing and/or cutting devices, etc.

As shown in FIGS. 2-4, the adapter assembly 20 of the surgical instrument 10 includes a coupling mechanism 14, an outer tube 24 extending distally from the coupling assembly 14, and an outer housing, such as, for example, a rotatable knob housing 21 for manually rotating a distal end portion 24 b of the outer tube 24 and the attached surgical loading unit 30. The coupling mechanism 14 is configured to be operably coupled to the handle assembly 12 or a surgical robotic system (not shown) responsible for actuating the surgical instrument 10. The coupling mechanism 14 has a proximal housing 14 a (FIG. 3) configured to couple to a distal half-section 13 (FIG. 1) of the handle assembly 12, a distal cap 14 b attached to the proximal housing, and a plurality of drive assemblies supported in the proximal housing 14 a for transferring actuation forces from motors (not explicitly shown) of the handle assembly 12 to the surgical loading unit 30. For example, one of the drive assemblies is an articulation drive assembly 100 (FIG. 4) including a drive shaft 102 and a rotation gear 104. The drive shaft 102 is rotatably supported by the proximal housing 14 a and is configured to receive actuation forces from one of the drive motors of the handle assembly 12. The drive shaft 102 supports a gear 106, such as, for example, a pinion gear that is in meshing engagement with the rotation gear 104 (e.g., a spur gear). The rotation gear 104 is disposed about and fixed to a cam 108 of the adapter assembly 20. In aspects, various alternate types of gears and/or drive transfer mechanisms may be provided, such as, for example, belt drives, miter gears, bevel gears, helical gears, screw gears, or the like.

The outer tube 24 (FIG. 2) of the adapter assembly 20 may be an assembly including a proximal tube 24 a (FIG. 3) disposed within the knob housing 21 and a distal tube 24 b connected to the proximal tube 24 a. The proximal tube 24 a is rotationally and axially fixed to the coupling mechanism 14, and the distal tube 24 b is configured to rotate with respect to the proximal tube 24 a and with the knob housing 21 about a longitudinal axis “X” (FIG. 2) defined by the outer tube 24.

FIGS. 3-5 illustrate the cam member 108, which may be a tubular shaft or housing that extends through and is rotationally supported in the proximal tube 14 a of the outer tube assembly 24. The cam member 108 may be pinned or otherwise non-rotationally coupled to the rotation gear 104 of the coupling mechanism 14, such that the cam member 108 rotates with a rotation of the rotation gear 104. The cam member 108 has a tubular outer surface defining a proximal cam slot 108 a and a distal cam slot 108 b therein. The proximal and distal cam slots 108 a, 108 b are longitudinally spaced from one another and wrap around a central longitudinal axis defined by the cam member 108. The proximal and distal cam slots 108 a, 108 b each have opposite helical configurations. For example, the proximal cam slot 108 a may have a left-handed helical configuration, whereas the distal cam slot 108 b may have a right-handed helical configuration, or vice versa. In aspects, the proximal and distal cam slots 108 a, 108 b may each have the same handedness, such as left-handedness or right-handedness.

With reference to FIGS. 3, 4, 6, and 7, the adapter assembly 20 further includes a pair of proximal and distal ring members 110, 112 operably coupled to the cam member 108, a pair of articulation shafts 120, 122 operably coupled to the ring members 110, 112, and a pair of articulation links 150, 152 (FIG. 8) operably coupling the articulation shafts 120, 122 with the surgical loading unit 30. The proximal and distal ring members 110, 112 are each disposed about the proximal tube 24 a, with each having a ring body 110 a, 112 a and a projection 110 b, 112 b, such as, for example, a pin, extending radially inward from the ring body 110 a, 112 a. The ring body 110 a, 112 a of each of the ring members 110, 112 defines an annular groove 114, 116 in an outer surface thereof. A flexible ring-shaped snap retainer 118, 124 may be received in the annular groove 114, 116 to maintain the projections 110 b, 112 b fixed to the ring bodies 1120 a, 112 a.

The projection 110 b of the proximal ring member 110 extends through a first longitudinally-extending guide slot 126 (FIG. 7) in the proximal tube 24 a and is received in the proximal cam slot 108 a of the cam member 108. The projection 112 b of the distal ring member 112 extends through a second longitudinally-extending guide slot (not explicitly shown) in the proximal tube 24 a and is received in the distal cam slot 108 b of the cam member 108. The first and second guide slots 126 are disposed on opposite lateral sides of the proximal tube 24 a and ensure that the proximal and distal ring members 110, 112 do not rotate during rotation of the cam member 108. Due to the projections 110 b, 112 b of the proximal and distal ring members 110, 112 being received in the respective proximal and distal cam slots 108 a, 108 b of the cam member 108, rotation of the cam member 108 translates the proximal and distal ring members 110, 112 in opposite directions along the longitudinal axis “X” of the outer tube 24.

As best shown in FIGS. 3 and 4, the left articulation shaft 120 includes a proximal end portion, such as, for example, a left housing half 120 a having a semi-cylindrical configuration, and a distal end portion, such as, for example, an elongate bar 120 b extending distally from the left housing half 120 a. Similarly, the right articulation shaft 122 includes a proximal end portion, such as, for example, a right housing half 122 a having a semi-cylindrical configuration, and a distal end portion, such as, for example, an elongate bar 122 b extending distally from the right housing half 122 a. The right housing half 122 a may be longer than the left housing half 120 a, as will be described.

Each of the housing halves 120 a, 122 a of the left and right articulation shafts 120, 122 has an inwardly-extending, annular protrusion 134, 136 disposed at a proximal end thereof. The annular protrusion 134 of the left housing half 120 a is slidably received in the annular groove 114 of the distal ring member 112 due to the left housing half 120 a being shorter than the right housing half 122 a. The annular protrusion 136 of the right housing half 122 a is slidably received in the annular groove 116 of the proximal ring member 110. As such, longitudinal motion of the proximal and distal ring members 110 a, 112 is transferred to the respective right and left articulation shafts 122, 120 while allowing for the right and left articulation shafts 122, 120 to rotate about the proximal and distal ring members 110, 112 and with the knob housing 21 (FIG. 4).

An outer surface of each of the housing halves 120 a, 122 a has a longitudinally-extending ridge 128 (the ridge of the right housing half 122 a is not explicitly shown) extending outwardly. Each of the ridges 128 is slidably received in a corresponding longitudinally-extending channel or slot 130 defined in an inner surface 132 of the knob housing 21. The engagement of the ridges 128 of the left and right housing halves 120 a, 122 a with the channels 130 defined in the opposite sides of the knob housing 21 allows for the left and right articulation shafts 120, 122 to translate relative to and within the knob housing 21 while also forming a non-rotatable engagement with the knob housing 21 such that the articulation shafts 120, 122 are rotatable with the knob housing 21.

The left and right housing halves 120 a, 122 a of the left and right articulation shafts 120, 122 each further include an inwardly-extending projection or tab 138, 140 (FIG. 3) that extend through respective left and right longitudinally-extending guide slots 144 a, 144 b defined in the distal tube 24 b. The guide slots 144 a, 144 b in the distal tube 24 b allow for the left and right housing halves 120 a, 122 a to translate relative to the distal tube 24 b while non-rotationally coupling the left and right housing halves 120 a, 122 to the distal tube 24 b.

With reference to FIGS. 4, 8, and 9, each of the elongate bars 120 b, 122 b of the left and right articulation shafts 120, 122 has a proximal end portion 146 a, 148 a and a distal end portion 146 b, 148 b. The proximal end portion 146 a, 148 a of each of the elongate bars 120 b, 122 b defines an opening having received therein the respective tab 138, 140 of the left and right housing halves 120 a, 122 a to axially fix the left housing half 120 a to the left elongate bar 120 b and axially fix the right housing half 122 a to the right elongate bar 122 b. The left and right elongate bars 120 b, 122 b of the respective left and right articulation shafts 120, 122 extend distally through the distal tube 24 b and terminate distally at a distal end of the distal tube 24 b.

The first articulation link 150 (FIG. 8) has a proximal end portion 150 a pivotably coupled to the distal end portion 146 b of the left elongate bar 120 b, and the second articulation link 152 has a proximal end portion 152 a pivotably coupled to the distal end portion 148 b of the right elongate bar 122 b. In aspects, the first and second articulation links 150, 152 may be coupled to the first and second elongate bars 120 b, 122 b via intermediary shafts (not explicitly shown). The first and second links 150, 152 each have a distal end portion 150 b, 152 b pivotably coupled to opposite sides of a collar 32 of the surgical loading unit 30. As such, the opposing longitudinal motion of the first and second articulation shafts 120, 122, induced by a rotation of the cam member 108, pushes and pulls the corresponding first and second links 150, 152 to articulate the surgical loading unit 30 relative to the adapter assembly 20.

The surgical loading unit 30 is adapted to be attached to the distal tube 24 b of the adapter assembly 20 and may be configured for a single use, or may be configured to be used more than once. A pivot joint 26 (FIG. 9) is pivotably coupled to the distal tube 24 b and axially restrained thereto. The pivot joint 26 is configured to pivotably support the collar 32 of the surgical loading unit 30 thereto. The surgical loading unit 30 includes an end effector 34 supported on the collar 32. The end effector 34 includes an anvil plate 36 non-rotationally coupled to the collar 32, and a staple cartridge assembly 37 disposed in opposed relation with the anvil plate 36. The staple cartridge assembly 37 has a chassis 38 pivotably coupled to the collar 32 and a staple cartridge body 40 configured for removable receipt in a channel of the chassis 38. A knife rod (not explicitly shown) is translatable through the end effector 34 to cut tissue disposed therebetween. The knife rod is further configured to selectively open and close the end effector 34 and fire staples therefrom as it translates through the end effector 34.

In operation, with reference to FIGS. 10 and 11, to articulate the surgical loading unit 30, the drive shaft 102 of the articulation drive assembly 100 is rotated via an actuation of the handle assembly 12 (FIG. 1). The drive shaft 102 transfers rotational motion from the gear 106 fixed thereabout to the rotation gear 104. Since the cam member 108 is fixed to the rotation gear 104 (FIG. 5), the cam member 108 rotates with the rotation gear 104 about the central longitudinal axis “X” of the outer tube 24. As the cam member 108 rotates, the proximal cam slot 108 a of the cam member 108 drives the pin 110 a of the proximal ring member 110 through the proximal cam slot 108 a in a proximal direction and the distal cam slot 108 b of the cam member 108 drives the pin 112 b of the distal ring member 112 through the distal cam slot 108 b in a distal direction.

The proximal movement of the proximal ring member 110 drives a proximal movement of the right articulation shaft 122, in the direction indicated by arrow “A” in FIG. 10, due to the engagement of the right housing half 122 a of the right articulation shaft 122 with the proximal ring member 110. Similarly, the distal movement of the distal ring member 112 drives a distal movement of the left articulation shaft 120, in the direction indicated by arrow “B” in FIG. 10, due to the engagement of the left housing half 120 a of the left articulation shaft 120 with the distal ring member 112. As such, the right and left articulation shafts 122, 120 are moved from a first position (FIG. 10) corresponding to a non-articulated orientation of the surgical loading unit 30 (i.e., the surgical loading unit 30 is coaxial with the outer tube 24) to a second position (FIG. 11) corresponding to an articulated orientation of the surgical loading unit 30 (i.e., the surgical loading unit 30 is pivoted to a non-parallel angle relative to the outer tube 24, FIG. 9).

In particular, due to the first articulation link 150 acting as a pivotable coupling between the left articulation shaft 120 of the adapter assembly 20 and the left side of the surgical loading unit 30, and the second articulation link 152 acting as a pivotable coupling between the right articulation shaft 122 of the adapter assembly 20 and the right side of the surgical loading unit 30, proximal movement of the right articulation shaft 122 and distal movement of the left articulation shaft 120 drives an articulation of the surgical loading unit 30 in the right direction indicated by arrow “C” in FIG. 9. It is contemplated that a rotation of the cam member 108 in the opposite direction results in an articulation of the surgical loading unit 30 in the left direction.

To rotate the surgical loading unit 30 about the longitudinal axis “X” of the outer tube 24, the knob housing 21 may be manually rotated about the longitudinal axis “X.” Since the ridge 128 (FIG. 3) of the left housing half 120 a is captured in the left channel (not shown) in the knob housing 21, and the ridge (not shown) of the right housing half 122 a is captured in the right channel 130 (FIG. 4) in the knob housing 21, the left and right articulation shafts 120, 122 rotate with the rotation of the knob housing 21. The arcuate grooves 114, 116 in the proximal and distal ring members 110, 112 allow for the left and right articulation shafts 120, 122 to rotate relative to and around the proximal and distal ring gears 110, 112 during the rotation of the knob housing 21. Further, since the projection 138 of the left housing half 120 a is received in the left slot 144 a in the distal tube 24 b, and the projection 140 of the right housing half 122 a is received in the right slot 144 b in the distal tube 24 b, rotation of the left and right articulation shafts 120, 122 induces a corresponding rotation of the distal tube 24 b relative to the proximal tube 24 a, whereby the attached surgical loading unit 30 is also caused to rotate about the longitudinal axis “X.”

Persons skilled in the art will understand that the adapter assemblies and methods specifically described herein and illustrated in the accompanying drawings are non-limiting exemplary aspects of the disclosure. It is envisioned that the elements and features illustrated or described in connection with one exemplary aspect of the disclosure may be combined with the elements and features of another without departing from the scope of the disclosure. As well, one skilled in the art will appreciate further features and advantages of the disclosure based on the above-described aspects of the disclosure. Accordingly, the disclosure is not to be limited by what has been particularly shown and described, except as indicated by the appended claims. 

What is claimed is:
 1. An adapter assembly, comprising: a cam member defining a first cam slot and a second cam slot; an outer tube extending distally from the cam member and having a distal end portion configured to be coupled to a surgical loading unit; a first articulation shaft having a proximal end portion operably coupled to the first cam slot of the cam member, and a distal end portion configured to be coupled to the surgical loading unit; and a second articulation shaft having a proximal end portion operably coupled to the second cam slot of the cam member, and a distal end portion configured to be coupled to the surgical loading unit, wherein the first and second articulation shafts are configured to translate in opposite directions in response to a rotation of the cam member to articulate the surgical loading unit relative to the outer tube.
 2. The adapter assembly according to claim 1, further comprising: a proximal ring member disposed about the cam member and having a projection received in the first cam slot; and a distal ring member disposed about the cam member and having a projection received in the second cam slot, wherein the proximal and distal ring members are configured to move axially in opposite longitudinal directions in response to the rotation of the cam member.
 3. The adapter assembly according to claim 2, wherein the proximal end portion of the first articulation shaft is axially restrained to the proximal ring member, and the proximal end portion of the second articulation shaft is axially restrained to the distal ring member, such that the first and second articulation shafts are configured to move axially with the respective proximal and distal ring members.
 4. The adapter assembly according to claim 3, wherein the first and second articulation shafts are rotatable relative to and about the respective proximal and distal ring members.
 5. The adapter assembly according to claim 4, wherein the proximal ring member defines an outer annular groove therein, and the proximal end portion of the first articulation shaft has an annular protrusion slidably received in the annular groove.
 6. The adapter assembly according to claim 5, wherein the distal ring member defines an outer annular groove therein, and the proximal end portion of the second articulation shaft has an annular protrusion slidably received in the annular groove of the distal ring member.
 7. The adapter assembly according to claim 4, further comprising a knob housing disposed about a proximal end portion of the outer tube, wherein the proximal end portion of each of the first and second articulation shafts is non-rotationally coupled to the knob housing and axially movable relative to the knob housing.
 8. The adapter assembly according to claim 7, wherein the knob housing includes an inner surface defining a pair of longitudinally-extending slots, and the proximal end portion of each of the first and second articulation shafts has a longitudinally-extending ridge received in the respective pair of longitudinally-extending slots of the knob housing.
 9. The adapter assembly according to claim 7, wherein the proximal end portion of the first articulation shaft has an inwardly-extending protrusion, and the distal end portion of the outer tube defines a longitudinally-extending slot having received therein the protrusion of the first articulation shaft, such that the distal end portion of the outer tube rotates with the first articulation shaft about the longitudinal axis in response to a rotation of the knob housing.
 10. The adapter assembly according to claim 1, wherein the proximal end portion of each of the first and second articulation shafts is disposed about the outer tube and the cam member.
 11. A surgical instrument, comprising: a surgical loading unit; and an adapter assembly including: a coupling mechanism having a drive shaft; a cam member operably coupled to the drive shaft and defining a proximal cam slot and a distal cam slot; an outer tube extending distally from the cam member and having a distal end portion configured to be coupled to the surgical loading unit; a first articulation shaft having a proximal end portion operably coupled to the proximal cam slot of the cam member, and a distal end portion configured to be coupled to the surgical loading unit; and a second articulation shaft having a proximal end portion operably coupled to the distal cam slot of the cam member, and a distal end portion configured to be coupled to the surgical loading unit, wherein the first and second articulation shafts are configured to translate in opposite directions in response to a rotation of the cam member to articulate the surgical loading unit relative to the outer tube.
 12. The surgical instrument according to claim 11, wherein the adapter assembly further includes: a proximal ring member disposed about the cam member and having a projection received in the proximal cam slot; and a distal ring member disposed about the cam member and having a projection received in the distal cam slot, wherein the proximal and distal ring members are configured to move axially in opposite longitudinal directions in response to the rotation of the cam member.
 13. The surgical instrument according to claim 12, wherein the proximal end portion of the first articulation shaft is axially restrained to the proximal ring member, and the proximal end portion of the second articulation shaft is axially restrained to the distal ring member, such that the first and second articulation shafts are configured to move axially with the respective proximal and distal ring members.
 14. The surgical instrument according to claim 13, wherein the first and second articulation shafts are rotatable relative to and about the respective proximal and distal ring members.
 15. The surgical instrument according to claim 14, wherein the proximal ring member defines an outer annular groove therein, and the proximal end portion of the first articulation shaft has an annular protrusion slidably received in the annular groove.
 16. The surgical instrument according to claim 15, wherein the distal ring member defines an outer annular groove therein, and the proximal end portion of the second articulation shaft has an annular protrusion slidably received in the annular groove of the distal ring member.
 17. The surgical instrument according to claim 14, wherein the adapter assembly further includes a knob housing rotationally coupled to the coupling mechanism and disposed about a proximal end portion of the outer tube, wherein the proximal end portion of each of the first and second articulation shafts is non-rotationally coupled to the knob housing and axially movable relative to the knob housing.
 18. The surgical instrument according to claim 17, wherein the knob housing includes an inner surface defining a pair of longitudinally-extending slots, and the proximal end portion of each of the first and second articulation shafts has a longitudinally-extending ridge received in the respective pair of longitudinally-extending slots of the knob housing.
 19. The surgical instrument according to claim 17, wherein the proximal end portion of the first articulation shaft has an inwardly-extending protrusion, and the distal end portion of the outer tube defines a longitudinally-extending slot having received therein the protrusion of the first articulation shaft, such that the distal end portion of the outer tube rotates with the first articulation shaft about the longitudinal axis in response to a rotation of the knob housing.
 20. The surgical instrument according to claim 11, wherein the proximal end portion of each of the first and second articulation shafts are curved and disposed about the outer tube and the cam member. 